This invention relates broadly to refrigeration systems, and more particularly to refrigeration systems having reciprocating displacers in cylindrical pressurized vessels, such as Vuilleumier-cycle apparatus.
Many refrigeration systems employ an elongated, cylindrical vessel having a displacer slideably mounted therein making sealing contact with the inner wall thereof. In such systems a regenerator is often coupled between opposite ends of the elongated cylindrical vessel so that, when the displacer is moved toward one or the other end of the vessel, refrigerant fluid therein is driven through the regenerator to the opposite end of the elongated cylindrical vessel. Such a system is disclosed in U.S. Pat. No. 3,367,121 to Higa, for example.
In Vuilleumier-cycle apparatus, there are often two such vessel/displacer/regenerator systems interconnected such that first ends of the elongated cylindrical vessels are coupled via a conduit. One of the elongated cylindrical vessels is heated at its second end and the other is cold at its second end; thus, the heated vessel is said to have a high-temperature space at its second end and an intermediate temperature space at its first end, while the other vessel is said to have an intermediate temperature space at its first end and a low temperature space at its second end with the two intermediate temperature spaces being interconnected by the conduit. The displacers are interconnected by a linkage which moves them in their respective vessels in an appropriate phase relationship to produce the cooling. The pressure differences across the displacers are small, hence, very little mechanical power is required to drive the displacers except to overcome small frictional losses. In fact, the heat that is added to the system can in some cases drive the system without applying power to the linkage, except for getting the system started. However, in many cases, small amounts of power must be applied directly to the linkage to keep the system operating. This invention is concerned with providing an appropriate linkage between displacer units.
For further discussions of the Vuilleumier-cycle, as well as the Stirling cycle, and the Gifford-McMahon cycle, the following materials are hereby incorporated by reference: Paper by G. K. Pitcher and F. K. du Pre entitled Miniature Vuilleumier Cycle Refrigerator published in ADVANCES IN CRYOGENIC ENGINEERING, Volume 15, page 444 et seq., Plenum Press, New York, 1970; a paper entitled The Vuilleumier Cycle, by G. Prast delivered at the Third International Cryogenic Engineering Conference in 1970 and published at page 21 et seq. of the PROCEEDINGS OF THE THIRD INTERNATIONAL CRYOGENIC ENGINEERING CONFERENCE, Berlin, May, 1970, Iliffe Science and Technical Publishing Ltd., 32 High Street, Guildford, Surrey, United Kingdom, 1970.
A problem that has been encountered with refrigeration apparatus of the type described above is that moving linkages which move the displacers along the vessels often pass through dynamic seals of the sealed vessels and thereby provide a possible entrance for contaminating materials into the vessels. In addition, some such systems have required bearings and gears located within the cooler working volumes. Such mechanical elements must be lubricated, thus, introducing still other contaminants into the vessels. It is therefore an object of this invention to provide a linkage for moving displacers along refrigeration vessels with providing possible openings for contaminants or requiring contaminants to be introduced into the vessels for lubrication.
In some systems electromagnets are used to control the positions of the displacers in vessels, without having moving linkages passing through the walls of the vessels (see U.S. Pat. No. 3,774,405 to Leo). However, it is difficult for such linkages to obtain positive positional control of the displacers, and they sacrifice the reliability of mechanical linkages.
Some prior art systems involve the use of sealing members for allowing linkage rods, levers and the like to extend into the vessels. Such seals, however often fail and require replacement. Thus, it is yet another object of this invention to provide a durable linkage which requires less maintenance than the linkages of many prior art systems for moving the displacers in the vessels.
It is also an object of this invention to provide a refrigeration system having a displacer linkage which is both efficient, dependable, and economical to manufacture.